Dearie begin his legal career at Shearman & Sterling in 1969. Dearie subsequently worked as an Assistant United States Attorney in the Eastern District of New York, where he served in the Appeals Division from 1971 to 1974, as the Chief of the General Crimes Section from 1974 to 1976, Head Chief of the Office's Criminal Division from 1976-1977 and briefly as the Executive Assistant United States Attorney for the District in 1977.[4] He worked in private practice until 1980 before serving as the Chief Assistant United States Attorney until 1982, when he was appointed the United States Attorney for the Eastern District of New York by President Ronald Reagan, serving from 1982 to 1986, before being appointed to the federal bench, by the recommendation of New York Senator Al D'Amato.[5][3]